The invention relates generally to firearms, and, more particularly, to a device for loading a cartridge into a cartridge chamber of a barrel of an automatic small arm.
During cartridge loading, entrainment of a cartridge occurs via a bolt head on the front end of the bolt assembly of the weapon. A recess that forms a recessed percussion base can be situated on this front side of the bolt head. During reloading of the weapon, the uppermost cartridge of a magazine, the next cartridge of a horizontal belt feed, or the like, is brought into a feed position in front of the bolt head. A recoil spring pushes the bolt assembly and the bolt head forward. The cartridge is then moved forward together with the bolt assembly. During this forward movement, the cartridge is raised so that the rear end of the cartridge casing finally reaches the recess of the bolt head, if present. During subsequent forward movement, the cartridge is pushed into the cartridge chamber of the barrel. Because of the narrow tolerances between the engagement of the cartridge and the cartridge chamber, the cartridge is centered with respect to a center axis of the barrel or bore of the barrel. At the conclusion of the forward movement, the bolt assembly is connected to the barrel by means of a locking piece fastened on the barrel. This connection can be affected, for example, by rotation of the bolt head. The weapon is then in a loaded state.
The bolt assembly must then be centered with reference to the cartridge and the barrel. The centering of the cartridge relative to the bolt head is achieved by seating the rear end of the cartridge casing in the recessed percussion base of the bolt head. Substantial tolerances can be present between the bolt assembly and a housing that guides it to permit trouble-free functioning of the weapon even when heavily soiled. However, the tolerances between the engagement of the rear end of the casing and the percussion base of the bolt head must be close. The periphery of the percussion base must be countersunk, in order to facilitate entry of the cartridge into the percussion base.
A firearm, in which the barrel has a shoulder with a conical input opening behind the cartridge chamber, is described in U.S. Pat. No. 3,641,692. In that patent, the bolt assembly is introduced into the conical input opening during loading of the weapon. Substantial tolerances are present between the introduced bolt assembly and the shoulder. Centering of the bolt assembly with reference to the center axis of the barrel therefore occurs in the usual manner, namely, by the seat of the cartridge casing on the front end of the bolt assembly.
It is proposed in the small arm described in U.S. Pat. No. 3,225,657 to configure the outer surfaces of the front end of the bolt assembly to be conical. These outer surfaces come into contact with the also conically-shaped inside surfaces of a part coupled to the rear end of the barrel when the bolt assembly enters its forwardmost position to complete loading of the weapon. This engagement seals the barrel to the rear.
A cylindrical bolt assembly with extremely limited tolerances is known from U.S. Pat. No. 3,742,638.
U.S. Pat. No. 5,499,569 and U.S. Pat. No. 3,641,692 each includes an inner cone directly connected to the cartridge chamber to the rear which is engaged by an outer cone on the front side of the bolt assembly. In each case, however, the purpose of this cone is to prevent gas escape from the rear of the barrel. Centering is neither sought nor disclosed in these documents.
In accordance with an aspect of the invention, an apparatus is provided for use in a firearm. The apparatus includes a barrel having a center axis; a cartridge chamber; and a bolt assembly that can be displaced in the longitudinal direction of the weapon from a rearward position to a forward position to advance the cartridge into the cartridge chamber. The apparatus also includes a centering element rigidly connected to the barrel for centering the bolt assembly before the cartridge is completely introduced into the cartridge chamber as the bolt assembly moves from the rearward position toward the forward position. A center axis of the bolt assembly is not coaxial with the center axis of the barrel when the bolt assembly is in the rearward position. The center axis of the bolt assembly is coaxially aligned with the center axis of the barrel after centering by the centering element. The centering element comprises a cavity including recesses with outer surfaces which taper conically from a rear of the cavity to a front of the cavity.
In accordance with another aspect of the invention a firearm is provided which includes a barrel having a center axis; a cartridge chamber; and a bolt assembly mounted for movement from a rear position to a forward position to advance a cartridge into the cartridge chamber. The bolt assembly includes a center axis which is not in coaxial alignment with the center axis of the barrel when the bolt assembly is in the rear position. The bolt assembly further includes a bolt head defining a percussion recess. The percussion recess is dimensioned to receive a proximal end of the cartridge with clearance to permit transverse movement of the proximal end of the cartridge relative to the percussion base. The firearm also includes a locking piece adjacent the cartridge chamber for centering the bolt head as the bolt assembly moves from the rear position toward the forward position such that the center axis of the bolt assembly is substantially coaxially aligned with the center axis of the barrel. The center axis of the cartridge is not in coaxial alignment with the center axis of the barrel when the bolt head engages the cartridge. The center axis of the cartridge becomes substantially coaxially aligned with the center axis of the barrel after engagement of the bolt head and the cartridge but before the center axis of the bolt assembly becomes substantially coaxially aligned with the center axis of the barrel.
In accordance with another aspect of the invention, a method is provided for loading a cartridge into a cartridge chamber of a firearm. The method comprising the steps of: (A) advancing a bolt assembly in a longitudinal direction of the weapon; (B) engaging the cartridge with a bolt head of the bolt assembly at a first time when a center axis of the cartridge is not coaxially aligned with a center axis of the cartridge chamber and while a center axis of the bolt assembly is not coaxially aligned with the center axis of the cartridge chamber; (C) at a second time after the first time, centering the cartridge such that the center axis of the cartridge is in substantial coaxial alignment with the center axis of the cartridge chamber; and (D) at a third time after the second time, centering the bolt assembly such that the center axis of the bolt assembly is in substantial coaxial alignment with the center axis of the cartridge chamber.
Other features and advantages are inherent in the disclosed apparatus or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings.